Radio tuning mechanism



2 Sheets-Sk nn Q 0 1 INVENTOR.

, 62mm: 6 lP/f/MS G. c. PERKINS RADIO TUNING MECHANISM Filed Jul 'zg lsm Ill May 1', 194s.

i ll May 7, 1946. sic. PERKINS 2,400,052v

RADIO TUNING MECHANISM Filed July 2, 1942 2 Sheets-Sheet 2 61mm: 6! Pswmvs BY Fuzz.

' AITO NEY.

Patented May7, 1946 H 2,400,052 1 l RADIOTUNING Msonamsryr George C. Perkins, West Orange, assignor to Federal Telephone and Radio Corporation, a corporationoLDeiaware if a 0 I ApplicationJuly 2, 19:42, SerialNo. 449,451

7 Claims. (01. nitzuli This invention relates to tuning mechanisms for radio transmitters or receivers, and in particular to a means for setting the reactances of tunedcircuits associated with this type of apparatus.

It is old in the art toemploy so-called detent mechanisms for accurately presetting the capacitance values of gangedvariable condensers of radio receivers in order that a givenst'ation may belindexed and rapidly selected at the willof the operator. However, insofar as I, am aware, the

mechanisms of the prior art are ineflect arranged onthe periphery of a single disc or dial in much the same manner. as isdisclosed in Enderwood Patent 1,834,272. Without employing discs of excessive diameter, it is obvious that due to structural interference only a limited number of stops or detents can be positioned on the periphery reactance values, corresponding to the required predetermined frequencies, are nearly equal, the physical size of the stops will be so large that the position of-one stop will encroach on the space required by the other stop. In other words,..

one has the condition that two stops are required to occupy substantially the same space at the same time. In this specification and claims devices which yieldingl resist. the passa e of a a moving member througha given position in its path. arereferred to as detents. a 1 l It also willbe observed that in mechanisms of the class typified b the .Enderwood patent. the

detents are in fixed angular relationship to a struct a detent mechanism by which an operator may readily detect when detenting action has occurred. u

Still another object of the invention is to arrange a detent mechanism in which the detents are located along the length of a rotating shaft rather than on the periphery of a disc. During the operation of changing from one .predeterminedfrequency to another it is quite likely to .be" required thatone or more intermediate frequencies marked by stops or detents are'passed through. To enable the operator to know when the detent mechanism has reached the detent corresponding to the desired frequency, a suitable indicating means is provided. It is therefore a furtherobiect of this inven tion to combine a detentmechanism with an 0 indicating means to show when the desired frethereof. In the event that two or more of the a quency has been reached.

Additional object and advantages of this invention will become apparent to those skilled in this art by a; study of the following descriptions and claims, taken in connection with the drawings 0 showing a preferred embodiment and one modishaft and dial which rotates, at a slower: rate than the shaft which is under the direct control of the operator. If this difference in rotation is relatively large, as it may well be in cases where a very fine or vernier setting of the. dial is desired, the operator loses that sense of touch or 40 "feel which indicates that the step has :been

. engaged; Byplacing the ,detents on shafts which rotate atsubstantially the same or at greater rates than the operating shaft, the operator has this feel of adjustment which is so essential as a practical matter. f l

It is. therefore one purpose of this invention to arrange a detent mechanism in which any number of detents can be employed, regardless of:

limitations which may befimposed due to small 50 differences in predetermined frequencies.

fication of the invention, wherein: Fig. 1 shows a plan view of a detent mechanism, togetherwith gearing for adjusting the reactancesof the transmitter or receiver; a

Fig. 2 shows in side elevation ayiew of the mechanism of Fig. .1; n A A Fig. 3is an end elevation taken at section 3-3 ofFlg. 2 showing a gearing arrangement for driving the detent mechanism from the control shaft and also for operating a tuning dial; 1.

- Fig. dis a view of section l-l of Fig. 2showing the essential elements of the detent mechanism; and

Another object of the inventionis tolconstruct, a detent mechanism in which the various detents are placed on a shaft which rotates at substantiali the same rate as'the operating shaft.v

A further object of the invention is to con- Fig. 5 is a schematic wiring diagram illustrat- ;ing .a preferred manner of combining an indi-. cating lamp with aslightlymodified formof detent mechanism. a n

Referring to Figs. 1 and 2, S represents a drive shaft. by whichthe values of the various reactances of tuned radio circuits are adjusted, and

' also from which the drive of the detent mechanism is preferably accomplished through intermediate gearing. Bevel gears I, attached to shaft S,mesh with bevel gears 2 to drive the shafts 3. Connected to the latter are the variable reactances (Fig. 2) for adjusting the frequency of the tuned circuits. form of either variable inductance: or capaci;

tances. The reactances are not shown in detail, since their particular construction forms no part of the present invention.

These reactances may be in the produce a given reactance change.

It will be noticed that there is illustrated a stepdown ratio between gears I and 2. The greater this step-down ratio, the greater are the number of turns required by the operating shaft S to If a very large step-down ratio is required, each pair of gears I and 2 mag take the form of a worm and worm wheel. It will be obvious from the further discussion that the more turns shaft S makes for a given reactance change, the more closely spaced can be the predetermined frequencies while still retaining satisfactory detent action.

On shaft S is also mounted spur gear 4, which drives the shaft through intermediate gear 5. Attached to shaft 5 is gear I, which in turn rotates lead screw 8 through gear 9. Gears 4 and 6 maintain a 1 to 1 ratio between shafts S and 5, while gears I and 9 maintain a 1 to 3 ratio respectively between shaft 5 and lead screw 8. This ratio of gearing is merely shown by way of example, but in general it is desirable to have several rotations of lead screw to one rotation of shaft, The reason for this will be brought out hereinafter.

Mounted on shaft 5 are two gears, I4 and I5, for the purpose of eliminating any back lash which might otherwise be present in the gear train. Gear I4 is similar to gear 6 and gear I5 is similar to gear I, These gears, I4 and I5, are not fastened to shaft 5, but are constrained to tend to rotate thereon in opposite directions by means of spring I8. Actual opposite rotation does not occur since the gears are in mesh with gears 4 and 9. This reduction of back lash by spring-loading, as it is called, is old in the art and constitutes no part of the present invention.

Also attached to shaft S is spur gear I 0, which meshes with gear I I. Mounted on the same shaft as gear II and rotating therewith is spur gear I2, this later gear meshing with gear I3, on which an indicating dial 34 is mounted. The gear ratio of this last set of gearing is purely arbitrary, but in general there should be several revolutions of the driving shaft S to one revolution of the indicator dial.

On the lead screw 8 is mounted a traveling nut I1 and a contact arm I8, having a notched contact face I9, (Fig. 4) Arm I8 is pivotally mounted in a recess in nut II by means of bar 20, which passes through a hole in both the arm and the nut and extends parallel with shaft 8. Bar 20 also operates to keep the nut II from turning during rotation of the lead screw. During operation the nut I1 and arm I8 thus travel along shaft 8 with bar 28 as a guiding member. Suitable means such as spring 2I urges the contact arm I8 in a counter-clockwise direction, as seen in Fig. 4. The counterclockwise motion is limited by abutting surfaces 30 and 3| on pawl I8 and nut II, respectively, arm I8\ being free to yield downwardly.

Shaft 5 may be made of metal for the sake of rigidity, but in such case it has mounted thereon an insulating sleeve 22. On this insulating sleeve are mounted a plurality of contact members 23 each having an extension 24 adapted to mate with the notch III of arm I8. The several contact members may be fixed in any position along the length of the insulating sleeve, and with the extensions 24 directed along any radius. Figs. 1 and 2 show only two contact members to avoid complicating the figures. Any number of members may be employed depending on the number of required predetermined frequencies.

It was previously mentioned that it is desirable to produce several turns of shaft 8 during one rotation of shaft 5. In the present instance a 3 to 1 ratio is employed. This enables a relatively large longitudinal movement of the traveling nut on the lead screw, while at the same time the latter is provided with a relatively fine thread. In the present example, the lead screw is cut with 32 threads per inch, one turn of the screw thereby advancing the traveling nut a: of an inch. During one turn of the operating shaft S, the lead screw makes three revolutions and the traveling nut moves of an inch. During the same time that this movement takes place, there is also one complete rotation of shaft 5. The thickness of the extension 24 on each contact member 23 is in this example 1 of an inch. Likewise the thickness of arm I8 is 1 of an inch. It will now be obvious that during one revolution of shaft 5 together with members 23, arm I8 travels longitudinally of an inch. If in a given contact position, an extension 24 and arm I8 are so arranged that their surfaces are in alignment, it will be seen that a inch motion in either direction will be suflicient'to permit the cam to clear the pawl, and there will be no interference between them during consecutive revolutions.

The extension 24 on the contact members 23 can be either at the right or left hand side of the member. If all members are of the same hand the closest spacing of any two extensions 24 (and therefore of the predetermined frequencies) is determined by the width of the member 23. However, if adjacent extensions are at contiguous sides of their respective members they may be so placed that one side of one extension is substantially in a common plane with one side of another. In the above example wherein the lead screw has 32 turns per inch this is equivalent to two-thirds of a revolution of shaft 5. The members 23 cannot be in contact on the insulating sleeve 22, otherwise the indicating lamp 33 would give a false indication. A slight separation of the members is therefore necessary'to give the desired insulation between them. It is of course possible to vary the widths of the members and their extensions, the width of the arm, the turns per inch of the lead screv and also the gear ratios to obtain even closer settings than those given in the above example.

Bar 25, which also extends parallel to the other shafts of the mechanism, carries a plurality of adjustable blocks 28, each of these latter in turn being fixed to an insulating strip 28 carrying a spring contact 21. This contact -'hrough a circuit passing through the contact 21, the camshaped-member 23, an arm I8, nut I1 and lead screw together with a suitable voltage supply and a selective switch, operates a signal light to indicate when the desired frequency is reached during operation of the equipment.

Reference is now made to Fig. 5 which schematically shows this circuit together with a modification in structure. It will be noticed that the circuit is actually completed through three different contacts in series one between the nut and arm unit II-IB and the contact member 23 corresponding to member 23, another between said contact member and the spring arm 21' corresponding to spring 21, and the third'at a contact on the selective switch 32. When the operator wishes to select a givenfrequency he turns dial switch 32 to the proper position and starts turning shaft S until the indicating lamp 33 lights and the corresponding detent engages. In so doing he may pass through several detent positions,

each of, said positions being manually perceptible because of the increasedresistance to the turning ex shaft 8 while extension 24 of thecoiitact member-J3 infe'ac'h of. said positions is the extension-engaging, portion of arm Il aizailistthe pressure of spring 2| but he will know thatthey 7 do notcorrespond to the desired frequency since the indicating lamp does" notlight'up.

It will benoted that in Figs; 14 inclusive the member 23 has a cam-shaped face arranged to make or break the indicator connectionjbyjits contact with spring 21. This arrangement ermits, members 23 to be small, therebyaflording a saving in weight-important whenever the appaq ratus is used on aircraft. However, it isnot necessaryto make and break contact withjspri'ng 21,

. as the latter maytaketheform or aispring" arm 2l'Y tinually wiping a circularmemberffl as and the numberused are of course predetermined. 1,, Starting with'eitherflthe highest or the lowest 7 freuuencmthe transmitter istunedf by rotating shaft Suntilthe frequency of the desired value is obtained, In the case of a transmitter, this frequency can be found by a suitable wave ,ni'eter.

If the apparatusbe areceiver, thefrequency can be found bybeating the receiver withja signal of the desiredyalueuntil a ,ze'robeatnote is obtained, When the desired frequencyfhas been obtained, one of the contactmemsbers23stored at the end of shaft is shiftedfalong sleeve 22 until its extension 24 fits into notchl a of contact arm l8} as shownin Fig. 4. It is then clamped in position by means of screw 28. One of the blocks 26 is moved along shaft 23 until the contact spring 21 (or 21') mounted thereon engages member 23 (or 23').

The shaft S is then rotated until the next predetermined frequency is reached and the next adjacent contact member 23 is adjusted and set in the same manner as was the first member. Another block 26 is placed opposite this cam. This procedure is continued until the equipment has been tuned for all of the predetermined frequencies.

In operation the tuning shaft S is manually rotated, turning dial 34 in the usual manner and simultaneously adjusting the reactors on shafts 3. At the same time the nut I1 is shifted along feed screw 8, its position on the screw corresponding to the setting of dial 34. At the same time shaft 5 together with its insulating sleeve 22 and the various contact members 23 mounted thereon, is rotated in synchronism with screw 3 and shaft S, so that each extension 24 swings across the path of contact arm l8 once during each revolution of shaft 5. When the rotation of screw 3 brings arm l8 into alignment with an extension 24 the latter during its downward travel will contact the upper face of the arm, which will yield; but the pressure of spring 2| will produce sufficient resistance to the rotation of the extension 24 and shaft 5 to be noticeable to the operator who is turning shaft S. If he desires to stop the mechanism at that tuning point the registration of the nose of extension 24 with notch ill will permit highly accurate location of said mechanism at the desired setting. If he does not wishvto stop at that setting continued rotation of shaft 8 will shift extension 24 circumferentially beyond arm [3 and permit further unobstructed rotation of shaft 8." Thepitchof screw g I, the relative rate of rotation of said screwand shaft I, and the relative thickness ofextension Mandarin ll aresuch'thatwhen the extension completes its nextrotation after disengaging arm I3 11: will cle r said arm regardless of: the "direction in which the arm is shifted. The body 9' m: in arranged to contact with sprin of contact member 23 in the form illustrated in 21 ea nlum that the extension 24-is in position to engage an arm ll, 50 that a circuit through the signal'light 33 will be completed whenever said extension makes contact with the arm, provided switch 32 is set for that particular contact. The provision for circumferential asweii as longitudinal adjustment ofcontact members a greatly facilitates a high degree of accuracy in setting the contact members for adesiredreactance ,yalue, since circumferential I adjustment of a contact member 23 through a fraction of the circle along'which it'travels will have the same effect as a longitudinal adjustment through a corresponding fraction 'ertne distancetraveled by arm 3 during one revolution of shaft 5, thereby permitting very fine longitudinal adjustment by means of substantial circumferential adjust- I. erit of such member;

While I have shown anddescribed omyone s e ciflc embodiment andta slight modification of my invention,'itis tobe clearly understood that 1 changes and modifications as will occur to those skilled inthis art"are* contemplated and that I do not intend "to limit the invention except as whens claimed is: 1 i 1. Position indicating mechanism for radio tuning apparatus comprising a rotatable tuning shaft, a traveling contact member adapted to be driven along a straight path by said tuning shaft, a plurality of rotating contact members spaced from the shaft and located in spaced relationship adjacent the path of thetraveling contact member, means on said traveling contact member for yieldably interengaging any of said rotating contact members when the traveling member is in alignment therewith, thereby indicating a predetermined setting position of the tuning shaft; and means including gears driven by said tuning shaft for shifting the traveling contact member and for rotating the other contact members in synchronism with the rotation of the tuning shaft. 2. Position indicating mechanism asset forth in claim 1, in which each rotating contact member includes a contact extension traveling across the path of the traveling contact member, said rotating contact member being circumferentially adjustable to vary the circumferential location of said extension.

3. Position-indicating mechanism for radiotuning apparatus comprising a rotatable tuning shaft, a movable contact member, guide means for supporting said contact member for longitudinal movement thereon, means having a drive connection with the tuning shaft for moving the contact member along said guide means in synchronism with the rotation of said shaft, a plurality of detent means disposed in spaced relationship along said guide means, each engaging the contact member at a predetermined point in the cycleof rotation of the tuning shaft, an electrical signal and a selective switch having a plurality of contacts each connected to a detent means, whereby said electrical signal is selectively actuated whenthe contact-member is in engagement with a selected detent means.

4. Position-indicating mechanism for radiotuning apparatus comprising a rotatable tuning shaft, a feed screw, means comprising gear means driven by said rotating shaft for rotating said shaft and screw in synchronism, a contact shaft parallel and adjacent to the feed screw, means for rotating the contact shaft in synchronism with the feed screw, a traveling contact member having a threaded driving connection with the feed screw, adapted to travel in an axial direction in respect thereto, a plurality of cooperating contact members mounted in spaced relationship adJacent the path of the traveling memberand arranged to contact respectively the latter memher at predetermined settings of the tuning shaft, and means for adiustably mounting said plurality of cooperating contact members in spaced relationship along said contact shaft for rotation therewith in position to engage the traveling contact member when the latter is shifted by the -'ent points along said path for rotation about an axis parallel thereto in frictional engagement with said passing contact member, and means driven by said tuning shaft for moving said single contact member and rotating said plurality of contact members in synchronism with the tuning shaft. I

6. In a mechanism, according to claim 5, 1'0- tating contact members each adjustable by a translatory movement parallel to the straight path and by an angular movement in a plane perpendicular to said path so that each of said rotating contact members engages the passing contact member in a predetermined angular position, one of the engaging membersbeing' flexible andv formed as a socket and the otherbeing formed as a plug so as to permit the closing of an electric circuit in a predetermined. angular position;

7. In a mechanism according to claim 5, ro-

, tating contact members each adjustable by a than, said first arm to avoid engagement with the spring supported cam and the passing contact member, and a stationary spring contact arranged to engage the second arm of each of the rotating members, said two arms being offset with respect to each other along the axis of rotation to prevent, engagement between first arm and stationary spring contact, and to permit an electrical connection between stationary spring contact and rotating contact member in a predetermined angular position.

' GEORGE C. PERKINS. 

